The present invention is directed to a constant velocity joint (“CV joint”) and method of forming the same.
Two types of Rzeppa CV joints are commonly used in vehicles. The first type is a bell shaped CV joint and the second type is a disc shaped CV joint. The bell shaped CV joint is formed with a bell shaped outer bearing race having a bell shaft protruding from the crown of the bell. The bell and bell shaft are generally aligned symmetrically about a bell axis. Reference points may be forged on the bell and bell shaft for locating the bell axis during machining. The reference points allow precise and accurate machining of the bell shaped outer bearing race to provide a well balanced outer bearing race about the bell axis.
Disc shaped CV joints typically include a disc shaped outer bearing race, an inner bearing race, and stub shaft having a hub on one end. Alternatively, the disc shaped CV joint may be formed without the stub shaft and instead be flange mounted to a shaft. When assembled, the inner race fits within the outer disc race, with ball bearings located therebetween. A splined portion of the stub shaft then fits within the inner bearing race, specifically a splined hub on the inner bearing race. The CV joint provides articulation by the outer bearing race, connected to one shaft of the driveshaft, articulating relative to the inner bearing race and stub shaft, connected to the other shaft of the driveshaft. The outer bearing race and stub shaft are separately forged with each having their own axis. Therefore, during machining, the outer bearing race and stub shaft are machined about their respective axes, which may not be in alignment when assembled into a CV joint. To provide a CV joint with minimal noise, vibration, and harshness issues, the axes should be in alignment with one another when assembled and in alignment with the axis of the assembled CV joint. Another problem with disc shaped CV joints is that they are typically difficult to precisely and accurately manufacture, because each part is separately formed and machined. Other problems include finding the axis of each part during the machining process, especially the disc shaped outer bearing race. Each of the above problems makes it difficult to efficiently machine and assemble the CV joint so that the axes of each part are aligned and balanced to reduce or eliminate noise, vibration, and harshness issues. Another problem with disc type CV joints is that it currently is not possible to efficiently and repeatedly form the outer disc bearing race to near net shape tolerances so that the amount of machining is limited, especially machining of bearing races.